Control device



Oct 2l, '1941' w. R. McDowELL Erm. 2,260,033

CONTROL DEVICE Filed -June' 23, 1939 2 Sheets-Sheet l \zga iz 43 37 5v 2515,/l

lrwentos: WaltelF` R. vIcDox/velkY Russell A. Wnborne,

bvd

- Attorney l 'A1' .'I' '.If f" I K 2/ Y l A Oct' l21, 194l w. R. McDoWELL E-rAL 2,260,083

CONTROL DEVICE Filed June 23, 1939 2 Sheets-Sheet 2 Inventors Rgssell AQWinbome, b9 e. j

T eh` Attorney.

wfjlltzer` R. McDowell,

Patented ct. 21, 1941 2,200,083 CONTROL DEVICE Walter R. McDowell, Chicago, and Russell A. Winborne, Cak Park, Ill., assignors to Edison General Electric Appliance Company, Inc., Chicago, Ill., a corporation of New York Application June 23, 1939, Serial No. 280,796

(Cl. ZOO-138) 24 Claims.

This invention relates to a temperature control device, and more particularly to a temperature control device for electric circuits, such as a heating circuit, and it has for its object the provision of simplified, rugged and eiiicient device of this character which can be manufactured at low cost.

while not limited thereto, this invention has particular application in controlling the energizing circuit of electrically heated devices so as to maintain a desired predetermined temperature and is particularly useful in connection with electric ilatirons.

In one of its aspects, this invention contemplates a new organization of parts in a temperature control device so as to increase the sensitivity of the device and to permit it to be assembled as a rugged unit which can be readily attached to a heating appliance, suchas an electric flatiron.

In another aspect, this invention contemplates the provision of means for readily adjusting the temperature setting of the control device and for providing an off position for the device at room temperature.

In carrying this invention into effect in one form thereof, a rugged unitary supporting frame is provided which has formed therein a supporting flange which is adapted to be mounted in good thermal relation with the device to be controlled, such as the sole plate of an electric iiatiron, and to which is firmly attached a relatively short thermal responsive element. Also mounted 0n the supporting flange but vertically spaced from said thermally responsive element is a resilient operating member, the free end of which is associated with a suitable vcircuit-controlling device. Threadedly supported by the frame is an u adjusting screw having a rounded end which is normally spaced from the operating member. The operating member, adjusting screw, and thermally responsive element are so arranged that movement of thethermally responsive element in response to an increase in temperature causes the operating member to be moved into engagement with the end of the adjusting screw and then about the end as a fulcrum causing a deflection of the free end of the operating member and actuation of the control associated therewith. In the preferred lform of'my invention, resilient means are associated with the free end of the operating member to cause it and its associated control switch t3 move with a snap action.

moving the end of the adjusting screw relative to the operating member.

For a more complete understanding of this invention reference should be had to the accompanying drawings in which Fig. 1 is a cross-section of a atiron to which has been applied the preferred embodiment of our temperature control device; Fig. 2 is a plan view of the structure shown in Fig. 1 with the cover of the iron removed; Fig. 3 is a detailed perspective view of the resilient operating member shown in Fig. 1; Fig. 4 is a detailed perspective view of the spring used with the adjusting screw; Fig. 5 is a detailed pei'- spective view of the unitary supporting structure; Fig. 6 is an enlarged perspective view showing details of the bridging contact supporting bracket; Fig. 7 is an enlarged sectional view showing the operative elements of the form of ourcontrol device shown in Figs. 1 and 2; Fig. 8 is a partial vertical section through a ilatiron showing a modified form of our temperature control device, in particular a slow acting temperature control device; and Fig. 9 is a plan view of the construction shown in Fig. 8 with the cover of the iron removed.

Referring to the drawings and particularly to Figs. 1 and 2, this invention has been shown in one form as applied to an electric ilatiron. It is to be understood, however, that this invention is not limited to this application but has general application.

The particular electric 'iron illustrated comprises a heavy body member or sole plate I0 made of a suitable heat-conducting material, such as cast iron or aluminum, and within which is cast a suitable electric heating unit II. Although any heating unit may be used, it is preferred to u se a heating unit of the type described and claimed inthe United States Patent No. 1,367,341 to C. C. Abbott, dated February 1, 1921.

Briefly, this unit comprises an outer metallic sheath I2 in which a helical heating resistor I3 is embodied in a compacted mass of heat-conducting, electricalinsulating, refractory material I4 such as magnesium oxide. The heating unit II is substantially U-shaped with its terminals brought vout at the rear of the iron asishown in Fig. 2. VThe upper portion of the body member or sole plate I0 is enclosed by a cover I5 resting on a shoulder I6 provided for it in the sole plate, the cover being suitably secured to the sole plate by means of screws (not shown) and having attached thereto a suitable handle I'l. Also provided on the cover I5 are binding posts I8 Temperature adjustment is readily obtained by which are adapted to be connected to the terminals of the'U-shaped heating element provided within a suitable plug guide I9 attached to both the cover and the handle of the iron. It is to be understood that these details of the electric iron are merely illustrative and form no part of this invention.

In accordance with this invention, a rectangularly shaped recess 2| is provided in the body member or sole plate Il)V and provided in this recess integral with the sole, plate is a boss 22 upon which a temperature control device is adapted to be firmly mounted. As shown in Figs. l and 2, the boss 22 is arranged in the longitudinal center line of the recess and adjacent the end of the recess nearest the front or toe of the iron. Mounted on the boss 22 by means of screws 22a. is our improved control device comprising an association of operating elements,

including a relatively thin resilient operating member 33, a bimetallic temperature responsive element 3|, and an adjusting screw carried by a unitary supporting frame 23. It is to be observed that by means of the recess4 2l and boss 22 the unitary control device assembled as a unit on frame 23 is mounted in direct thermal relation with the heated body and in close proximity to the surface the temperature of which is to be controlled. The frame 23 is fabricated from a single piece of metal in order to reduce manufacturingcosts and' to provide a unitary supporting structure. As shown in Fig. 5, the framev comprises a substantially horizontal supporting ange 24 and a pair of vertically extending end wall portions 25 and 26 between which extends a substantially horizontal top wall portion 21.

'In order to increase the ruggedness and rigidity of this frame structurereinforcing flanges 28 and 29 are provided .along thelfront and back edges of th end ,wan 25, the top wan 21 and the iiange 24.

'Ihe temperature responsive element of our improved control device comprises a relatively short bimetallic element13| f irmly 'attached at one end to the supporting ange 24 of the trame 23. The bimetallicv elementl consists of two strips of metal having dissimilar coeicients of expansion, such stitute a fulcrum against which the operating member is adapted to bear.

.It will be observed that upon an increase in I temperature theibimetallic element 3| will be lengths of the blade 3| and the member 33. Thisv may be more clearly understood by referring to deected upward against the resilient operating member 33. This upward movement of the blade 3| causes a similar upward movement of the operating member until it engages the rounded end 38of the adjusting screw 31. Further upward movement of the bimetallic blade causes a ,rotation of the operating member about the roundedend of the adjusting screw as a fulcrum so as to cause a downward deflection of the free end of the operating member.

The deection of the operating member, which is a measure of the sensitivity of the control device, depends upon the resultant deflection of the bimetallic element 3| which may be dened as the free deflection of the blade for a given temperature change reduced by the restraining force exerted by the resilient' operating member. It

has been found that this resultant deflection is greater when the bimetallic blade is appreciably Fig. 7 in which'it will be observed that if the blade 3| were of such a length that its boss 35 lay directly below the rounded end 38 of the as Invar. and steel, the strips being securely braz'ed o r welded together lengthwise and arranged so that' an increase in temperature causes an upward deection of the bimetallic element.

Spaced f rom the. thermally responsive member 3| by means of a spacer 32 is a relatively thin re.

silient operating member 33 /which is also xed at one end to the supporting'ange 24.- Both the operating member and the bimetallic element are constructed and arranged'to pass-through an opening 30 provided in the end wall 25 and to l extend .longitudinallyJ of the frame' 23 in substantially parallel spaced relation. Provided in the free end of the .bimetallic blade3`| is a boss 35 which is adapted to engage the operating member 33. vided to separate the bimetal blade Vand the operating member is sumciently thick to .permit point or line contact at the point where the boss 35 engages the member 33. A pair of rivets 34 is lemployed to firmly mount the operadjusting screw 31, no useful motion would result for on an increase in temperature the bimetallic blade would expand its energy against the end 38 of the rigidly supported adjusting screw 31 and the free end ofthe loperating member would 4have zero deflection. Likewise, a bimetallic blade of zero length would result in no deflection of the free end of the operating member. It is thus apparent that a bimetallic blade length exists between these limiting. conditions which will produce a maximum deection. In accordance with this invention it is preferredto have a bii metallic element which is relatively short with respect tothe overall length of the operating member and it has been found that an element having an eective length equal to substantially 0.8 the length of the section of the'operating member between the bearing point 32a and th@ point o! contact between the operating memberl and the fulcrum 38-wil1 produce a maximum Thel spacer 32 whichJ is pro- While this is' the preferred bimetallic'blade ating member 33, spacer'32 amd bimetallic element 3| upon the supporting ange 24.

Arranged in the top wall 21 of the frame 23 is an aperture 36 into which is threaded an adjust- J ing screw 31 having a rounded end '33. This rounded endI 38 is normally spaced from' the operating member 33 but is adapted to be engaged by the operating niernbersoas to conf-75, sition of the lulc deflection of the free end of the operating mem ber and hence improve the sensitivity of the control device. In other words, referring to Fig. 7,

it has been found that the maximum deection is produced when L1 is substantially' of L.

length, it will be understood that otherv blade lengths may be used where a less sensitive control deviceis desired or adequate.

It will bejobserved that the extent of the up-4 ward movement of the bimetallic bladeA required to cause a downward deflection of the free end of the. operating member depends/upon the potormed by the rounded end 38 of the adjusting screw 31. By means of the threaded relation between the ladjusting screw and the frame 23, the position of the rounded end 38 may be varied. The screw 31 is adjusted by means of a knob or handle 38 mounted thereon so as to be accessible from the outside of the cover plate I of the iron. Intermediate the ends of the adjusting screw 31 is a knurled portion 40 upon which is pressed a stop plate 4|. This plate 4| is adapted to engage an integral tang 42 provided on the frame 23 adjacent the opening 36. By means of this arrangement the range of movement of the adjusting screw may be limited. A spring 43 is provided for the adjusting screw so as to provide a positive bias for all positions of the screw and take up any play or lost motion between the threads on the screw and frame '23. In addition, the spring functions to hold the adjusting screw verticalv 4 of the support.

Provided in the top wall 21 of the frame 23 is an opening 5l which is adapted to be covered by a contact-supporting plate d8. The plate 48 consists of a plurality of sheets of mica, or some similar suitable insulating material, and is attached to the top wall 21 by means of rivets 49. Mounted in the contact-supporting plate is a pair of spaced contacts 50 which are adapted to project through the opening 41 in the top wall 2i. A pair of suitable supply leads 5| and 52 are secured to the contacts 50. Preferably these members will be formed of relatively thin metallic strips, as shown, and preferably they will be directed to the under side of the insulating plate 48 through suitable apertures or slits provided in the plate, as is clearly shown in Figs. 1 and 2. It will be observed that the leads 'are connected so that the xed contacts form a part of the circuit between the prongs I8 of the supply terminals and the heating element |I. While the leads are in this instance connected in the heating circuit of a flatiron, it is to be understood that they may be connected in any circuit to be controlled or in a controlling circuit for a circuit to be controlled when the control device is used in other arrangements.

A bridging contact 53 for bridging the fixed contacts 5U is carried by the free end of the resilient operating member 33. The bridging contact 53 is carried by a U-shaped bracket 54 which is firmly secured to the operating member 33 by means of rivets 55. The bracket 54 is electrically insulated from the operating member by means of sheetsof insulating material 56 formed of any suitable insulating substance such as mica. As shown in Fig. 6, each of the legs of the bracket 54 has provided therein a slot 51 adapted `to receive projecting portions provided on the contact member 53 and to form a support therefor. Each slot 51 is provided with a curved surface 58 per.

mitting pivotal movement of the contact member 53 about an axis parallel with the operating member 33. Provided on one leg of the bracket 54 are two surfaces 53 which act as stops for the contact 53 to limit its pivotal'movement. This arrangement provides for a free oating contact which will positively and simultaneously break the electrical circuit at the two spaced contact points 50. 'I'he bridging contact 53 is shown provided with a contacting surface formed of a precious metal, such as line silver, which is secured in any suitable manner to a backing 6| formed of any suitable common metal, 4such as bronze.

The arrangement of the bimetallic blade 3| and the operating member 33 in our improved control device is such that when the temperature is below a predetermined maximum the contact 53 will be held in engagement with the fixed contacts 50, whereas when the temperature has been increased to a predetermined maximum the bimetallic blade will cause the free end of the operating member to deflect downwardly to move the bridging contact away from the iiXed contacts. In assembling the bimetallic blade and operating member the spacer 32 is of such thickness and the boss 35 on the bimetallic blade is of such height that with no force exerted on the operating member by the adjusting screw the bimetallic blade exerts an initial force against the operating member. In addition, the xed contacts are positioned so that with no force applied on the operating member by either the adjusting screw or the bimetallic blade they will be engaged by the bridging contact carried on the operating member. In this manner an initial Contact pressure is produced between the bridging contact and the xed contacts.

In order to limit the movement of the operating member and hence the bridging contact away rom the xed contacts and thereby to increase the switch sensitivity, a stop 62 is provided which comprises a substantially L-shaped bracket the horizontal portion of which is provided vvith a curved surface 63 forming a base against which the end ofrivet 55 is adapted to bear. Provided in the vertical portion of the L- shaped bracket is a slot 64 and directly below this slot is a tapped opening (not shown). The L-shaped bracket is adapted to be adjustably attached to the frame 23. To accomplish this, a bracket 65 depending from the ange 28 is integrally formed on the frame. Provided in the bracket 65 is an elongated slot 66 and provided on the inside edge of the flange 28 directly above the slot E6 is a boss 61. In assembling the stop, the bracket is inserted in the opening 41 provided in the frame 23 in such a manner that the boss 61 provided `on the frame is inserted in the f slot 64 provided on the vertical leg of the bracket.

i The screw 68 is then inserted into the elongated opening 66 and threaded into the tapped hole provided in the bracket. By sliding the bracket up or down while the elements are in this position and the screw 68 is not tightened, it can be adjusted to its proper position. After it has been so'adjusted, the screw 68 is tightened and maintains the bracket in its adjusted position.

In the preferred form of this invention, resilient means are provided for moving the bridging contact with a snap action. The resilient operating member 33 is provided at its free end with a knife-edge 68as shown in Fig. 3, and the 14 which receives the rounded bearing end 15 of an adjusting stud 16 threadedly supported in the end wall 26 of the frame 23. By means of the adjusting stud'16, the tension of the spring can be varied and, by means of the nut 11, the stud may be secured in such a position.

The compression spring 1l! functions to move the operating member quickly and with a snap action between its switch-opening and switchclosing positions. Best switch action is obtained when the knife-edge 66 snaps an `equal distance above and below the imaginary line drawn through the bearing 13 and the end 36 of the adjusting screw, this imaginary line constituting the neutral or center line of the device. Referring to Fig. 7, it will be observed .that since vthe screw 31 is adjustable an innite number of must be exerted by the compression spring 10 in order'to maintain a predetermined temperature, differential or amplitude. This increased compression spring force or end thrust results `in more pressure being exerted against either the contacts 56 or the stop 62 directly after the snap occurs thereby increasing the stability of the control device.

indicia will be arranged on the cover I5 so as to,

indicate the proper setting of the adjusting screw for best operation while ironing various fabrics,

neutral lines is possible depending upon the locamove equal distances about a neutral line at only one temperature setting. But the switch action of our improved control device is not impaired by this fact for the flexibility of the resilient operating member 33 makes it possible to obtain good performance even though the knife-'edge snaps unequal distances about a particular neutral line. In the preferred arrangement, the compression spring, 1@ is inclined at an angle to the resilient operating member` 33 as shown in Fig. 1. This initial inclination permits the knife-edge 69 to move equal distances about a center line determined by the position of the adjusting screw .at an average temperature which is approximately the mean of the extreme temperatures of the operating temperature range. With this construction and arrangement the knife-edge will operate above the center line for the lower temperature settings of the adjusting screw and below the center line for thel higher temperature settings, thus holding the displacement of the knife-edge to a minimum for any temperature setting within the operating range.

lThis is desirable since a relatively large displacement of the knife-edge from the neutral line results in a weakening of the snap action and a reduction in the amplitude of the switch.

By means of the adjusting stud 16, the range between maximum and minimum temperatures may be adjusted as pointed out in greater detail in the United States Reissue Patent No. 16,654 to A. Lewerenz. It is to be observed that adjustment of the stud 13 varies the end thrust exerted by the spring- 1@ on the resilient operating member 33.

To insure stability of the control device, that is, less tendency for the electrical contacts to such as silk, WOOL cotton, linen, etc. The rotation of`the adjusting screw spaces the rounded end thereof a predetermined distance away from the operating member 33.- With power supplied to the terminals I8, the heating coil ll of the iron is energized and, as the sole plate Hl heats up, heat is transmitted to the relatively short bimetallic element 3l by means of conduction through the boss 22 and convection currents within the recess 2l. strip firmly attached in good thermal relation with `respect to the surface the temperature of which is to be controlled, rthe minimum amount of thermal lag is encountered and the sensitivity of the control device thereby improved. In addition, by using a short, bimetallic blade, no comoperating blade so that it will have come in con- I member.

prematurely open or close due to rota-tion of the entire device or due to vibration or shock, the members supported by or acting on the operating 'member 33 are made as light'as practicable and the resilient member is stiffened near its knifeedge 69 preferably by some means which does not add to its weight and which permits the use of end thrusts of relatively large magnitude. In our preferred arrangement-the` free end of the operating member is embossed between the point of contact of the rounded end 38 of the adjusting screw 31 and the point of attachment of the tact with the rounded end 36 of the adjusting screw. A further increase in temperature causes the bimetallic element to rotate the operating blade around the rounded end of the adjusting screw'as a fulcrum thereby producing a downward deflection of the frce end of the operating This downward deflection is at first resisted by the spring 16 but upon the occurrence of the predetermined desired temperature a sumcient force is exerted on the operating member by the bimetallic element to overcome the force exerted by the spring 1@ and the end of the operating member starts to move downward. As it moves downward, the opposing force exerted by the spring 10 decreases and theoperating member rapidly accelerates and moves at a high speed until it strikes the stop 62. The heating circuit is thus quickly opened and the temperature of the heating device begins to decrease. With this decrease in temperature, the bimetallic blade begins to move downwardly and the force exerted by the blade onthe operating member is reduced causing the member to move in a counterclockwise direction about the rounded end 38 of the adjusting screw. Upon the occurrence of a certain minimum temperature, the operating member and its `associated bridging contact will be snapped to their closed circuit position by the spring 16.

Considering the operation of the control device in a different light and referring to Fig. 7,

By using a short bimetallic it .will be noted that the initial deilection of the bimetal causes the operating member to move upwardly against the end of the adjusting screw.

This movement of the operating member results broken. It is evident, therefore, that the position of the adjusting screw 31 determines the pressure stored up in the contacts and subsequently released. Temperature range is thus accomplished by causing'jvariations in the stored contact pressure through variations in the position of the end of the adjusting screw. y

In temperature control devices of the type un der discussion, it is often desirable to have'an oi position, that is, a position wherein the associated switch may be moved to its opened position irrespective of the temperature of the device being controlled. In our simplied control device, such an oi position is obtained by advancing the vadjusting screw 31 until the pressure it exerts against the operating member 33 is suilicient to produce a rotation of the operating member about the point of cont-act between it and the boss 35 of the bimetallic element. It Will beobserved that this rotation of the operatv ing member causes a downward deection of the free end of the member and this deflection is suflicient to cause the member and its associated bridging contact to be snapped to its open position. 'This open position will be maintained as long as the adjusting screw is maintained in its abnormal relation to the operating member corresponding to the off position.

In Figs. 8 and 9 is illustrated a modiiied form of our temperature control device. Parts corresponding to parts illustrated in Figs. 1 and 2 are indicated by the same numerals. It will be observed that the construction illustrated in Figs.

" 8 and 9 is similar to that described above except that the snap action .spring 10 located at the end of the operating member 33 is omitted. It is apparent, therefore, that the essential difference in this modified form otour invention is that the arrangement illustrated is a-slow-acting type of temperature control device. Additional structural changes are also illustrated in Figs. 8 and 9. It will be noted that a wire spring 19 is provided around the adjusting screw 31 in place of the U-spring illustrated in Fig. 4. In addition, only a single fixed contact 80 is mounted on the support 23. This xed contact is adapted to cooperate with a movable contact 8| mounted on the end of the operating member 33. It will be vobserved that ribs 18 are providedin the operating member in this modied form of temperature control device. These ribs'are not essential in this form of our invention and may be omitted.' However, when used, they serve to stiften the operating member and thus afford resistance to vibration and shock.

The manner in which this modied form of temperature control device operates is thesame -in all respects as that described with the form that the electrical connection in this instance is broken slowly instead of with a snap action.

While we have described our invention in connection with a flatiron, it will be apparent that it is applicable to any device in which it is desired to control an electric circuit in response to changes in temperature. We do not desire our invention to be limited to the specic embodiments shown and described and intend in the appended claims to cover all modifications thereof within the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a control device, a resilient operating member, control means actuated by said operat- A ing member, thermally actuated means associated with said operating member and arranged to cause movement thereof in response to temperature changes, means forming a fulcrum normally spaced from said operating member for eiecting the movement thereof to control the temperature at which said control device is actuated, and means associated with said fulcrum means for adjusting thev position thereof relative to said operating member whereby the temperature at which said control device is actuated may be regulated.

2. In a control device, a resilient operating member, control means actuated by said operating member, thermally actuated means associated with said operating member and arranged to cause movement thereof in response to temperature changes, a pivot spaced from said operating member at temperatures substantially below a `controlling temperature, and means for adjusting said pivot in the plane of movement of said operating member for controlling the movement of said operating member in response to movement of said thermally actuated means illustrated in Figs. 1 and 2 with the exception 15 so as to preselect the controlling temperature at which said control means are actuated.

3. In a control device, a resilient operating member, control means actuated by said operating member, thermally actuated means adapted to engage said operating member to cause movement thereof in response to temperature changes, and adjustable fulcrum means normally spaced from said operating member, said fulcrum means being engaged by said operating member and thereby effecting the movement of said operating member to control the temperature at which said control means are actuated.

4. In a control device, a resilient operating' member, control means actuated by said operating member, a thermal motor associated with said operating member and arranged to cause movement thereof in response to'temperature changes, an adjustable fulcrum against which said operating member is adapted to bear, said fulcrum being spaced from said operating member during a portion of the movement of said operating member, and means for-adjusting the position of said fulcrum relative to said operating member so that the temperature at which said con'- trol device is actuated may be regulated.

5. In a temperature control device, a resilient operating-member having one end fixed, its opposite end free to move and being constrained intermediate its ends by two fulcrums one of. which is movablel in response to temperature changes, elastic means bearing on said free end of @said resilient operating'member, said elastic-means being pivotally mounted and arranged to subject said operating member to' a forcev to cause said free end to move quickly and with a snap action said operating member to control the temperasaid support in spaced relation with respect to between two limiting positions upon a predetermined movement of said one fulcrum inresponse to a predetermined temperature change.

6. A temperature responsive control. device comprising a resilient operating member fixed at one end and free to move at its opposite end, control-means associated with said free end, thermally responsive means engaging said operating member intermediate its ends so as to cause1 movement of said operating member in response 10 to temperature changes, means spaced from said operating member at temperatures substantially below a predetermined-'temperature and positioned to be engaged by said operating member after a predetermined movement thereof to form a fulcrum about which said operating 'member pivots to actuate said control device upon the occurrence of said predetermined temperature,v and means associated with said last mentioned means for varying the spacing thereof from said member in order to preselect said predetermined temperature at which said control device is actuated.

7. In a temperature control device, xed contact means, a resilient operating member iixed at one end and having its opposite end free toA move, contact means mounted on the free end of said operating'member and adapted to engage said xed contact means, thermally respon- I sive means associated with said operating member and adapted to cause movement of said operating memberin response to changes in temperature, resilient means for producing an initial contact pressure between said `contact means, and means for eiiecting the movement of `ment of said free end, resilient means associated with said free end of said operating meinber for actuating said control meanswith a snap. action, a fulcrum adapted to be engaged by said operating member intermediate the ends of said member, heat responsive means engaging. said operating member intermediate s aid iixed end and said fulcrum and adjacentsaid fulcrum, said heat responsive means adapted to move said operating` member into engagement` with said fulcrum and pivot said member about said Y. fulcrum soV as to cause said control means to be actuated with a snap action by said resilient means, and means for vertically adjusting the position of'said fulcrum relative to said operating member whereby the temperature at which said control' means are actuated may be varied.

' 9. In a thermostatic switch having a support, an operating member having ,one end yixeciV to said support, a switch actuated by said operating member, an .adjusting screw having an end which extends through said support vand constitutes' a fulcrum for said operating member, I and a relatively short vbimetallic element fixed to minim adjustin screw is brought into engagement with said operating member and extending throughout its length in a direction substantially parallel to said operating member, said bimetallic vmember having a boss on its free end which is adapted to engage said operating member so that movement of'said element in response to changes in temperature produces rotation of said operating member about the end. of said adjusting screw as a fulcrum and actuation of said switch.

l0. In a control device, va resilient operating member, control means actuated by said operating member, a thermal element associated with said operating member andarranged to cause, movement thereof in response to temperature changes, a fulcrum against Awhich said operating member is adapted to bear and about which said member is rotated to actuate said control means in response to the occurrence of a predetermined temperatureand means for adjusting the position of said fulcrum relative to said operating member to control the temperature at which said control means is actuated, said fulcrum in one of its adjusted positions being brought into engagement with said operating member and causing said member to be rotated about the point of association of said operating member and said thermal element as a fulcrum to provide a mansupport in spaced relation to said element and adapted to'be engaged by said boss whereby movement of said thermal element causes movement "of said operating member, switch means adapted to be actuated by movement of said operating member, an adjusting screw threadedly mounted in said support and lying between the free end of said operating member and the point of contact ofsaid boss, a rounded end onsaid adjusting screw normally spaced from said operating member but adapted to be engaged by said member whereby movement' of said operating member/by said thermal. element in response to temperature changes causes said member to engage said rounded end of said adjusting screw andpivot thereabout at`a predetermined temperature to actuate said switch means, and means for ,adjusting the position of said rounded end of said adjusting screw relative to said operating member to provide a range of temperature settings, between a predetermined minimum temperature and a predetermined maximum temperature, said adjusting means being movable to a positionQbeyond that corresponding to said temperature whereby said end of said 'in response to changes intemperature, an operating, member arranged in substantially spaced parallel lrelation with respect to ,said bimetallic element and having one end free to move, control means 'adapted to be actuated by moveme tof said Afree end of said operating member, anI elastic member engaging the free end of 'said operatingimember and arranged to cause said voperating member to move quickly between two positions whereby said control means may be actuated with'a snap action, an adjusting screw having an end adapted to be engaged by said operating member at a point intermediate the ends of said member, and a boss on the free end of said bimetallic blade adapted to engage said operating member so that movement of the free end of said bimetallic blade in response to temperature changes causes movement of said operating member into engagement with said end of said adjusting screw and thereabout as a fulcrum to cause actuation of said control means.

13. A temperature control device comprising a support, an operating member fixed on said support and having one end free to move, control means actuated by movement of said operating member, an adjusting screw mounted in said support and having a rounded end adapted to be engaged by said operating member at a. point intermediate its ends, means for actuating said adjusting screw to adjust the position of said rounded end relative to said operating mem, ber, heat responsive means engaging said operating member intermediate its point of support and the point of contact of said adjusting screw and adjacent said latter point so that movement of said heat responsive means in response to changes in temperature causes rotation of said operating member about said fulcrum and actuation of said control means, and resilient means comprising a spring member adjustably mounted on, said Support and bearing on said I'ree end of said operating member' for effecting movement of said control means with a snap` action.

14. A temperature control device for a heating appliance comprising a support adapted to be firmly attached to said heating appliance, an adjusting screw threaded into said support and extending therethrough, a relatively short bimetallic blade having one end xed to said support and its other end free to move in response to changes in temperature, a boss formed in the free end of said bimetallic blade, an operating member having one end fixed to said support and the other end extending in a direction substantially parallel to said bimetallic blade, said operating member lying between said boss and the end of said adjusting screw and adapted to engage the end of said screw at a point intermediate the ends of said member and to be engaged by said boss intermediate its xed end and the point of contact with said adjusting screw, a switch adapted to be actuated by movement of the freel end of said operating member and an elastic member engaging the free end of said operating member to cause said member to move quickly between two positions wherebysaid switch may be actuated with a snap action.

15. A temperature control device comprising a support, an operating member having one end fixed to said support and its opposite end free to move, a knife edge bearingl on said free end of said member, resilient means bearing on said knife edge for eiecting movement of said free end of said operating member with a snap action between two limiting positions, bosses in said operating member adjacent said free end to increase its rigidity so that the end thrust of said resilient means may be increased for a given amplitude, switch means actuated by movement of said operating member, means for moving said operating member in response to changes in temperature comprising a heat responsive member engaging said operating member intermediate its ends, and means for effecting the movement of said operating member to control the temperature at which said switch means are actuated, said means comprising an adjustable fulcrum constructed and arranged to bear on said operating member at a point intermediate its free end and the point of contact of said heat responsive member and adjacent said latter point.

16. A temperature control device comprising a frame having two endwalls connected by a horizontally extending top wall, a pair of fixed contacts, an integral flange provided on one of said end Walls, a horizontally extending operating member having one end iixed to said flange, resilient means pivotally connecting said operating member to the other of said end walls, means in said other end wall for adjusting the tension -of said resilient means, an adjusting screw mounted in said top wall and having a rounded end adapted to extend therethrough to form a fulcrum for said operating member intermediateits ends, a bimetallic element xed at one end to said iiange and having a boss formed in its opposite end, said bimetallic member extending substantially parallel tc said operating member and being of such length that said boss will engage said operating member adjacent said adjusting screw at a point intermediate its xed end and the point oi contact of said rounded end of said adjusting screw.

-l7. In a temperature control device adapted to be assembled as a unitary structure and mounted in good thermal relation with the surface the temperature of which is to be controlled, a unitary frame having a pair of end walls, a top wall, and a supporting iiange integral with one of said end walls, a temperature responsive element xed at one end to said ange and having its opposite end ree to move and extending longitudinally of said frame through an opening in said one of said end walls, a resilient operating member vertically spaced from said thermally responsive element and arranged substantially parallel thereto, said operating member having one end xed to said supporting iiange and its other end free to move, a boss provided adjacent the free end oi said thermally responsive element engaging said operating member intermediate its ends so as to cause movement thereof in response to movement of said thermal element in accordance with temperature changes, switch means associated with saidtop wall of said frame and said operating member and adapted to be actuated by said operating member to circuit closing and circuit opening positions, resilient means associated with the free end of said operating member and said l other of said end walls of said frame for causing said member to move quickly between said circuit opening and said circuit closing positions. and means mounted in the top wall of said frame effecting the movement of said operating member so as to control the temperature at which said member causes said switch means to be actuated, said last mentioned means comprising an adjusting screw having a roisnded end against which said operating member is adapted to bear and about which said member is oivoted to actuate said switch means, said rounded end of saidadjusting screw being vertically adjustable with respect to said operating member between two limiting positions, one correspondingv to the maximum setting of the device and the other corresponding to an off position at room temperature.

18. In a temperature control device, a iixed contact, a resilient operating member nxed at one end and having its opposite end free to. move, a movable contact associated with said free end of said operating member and cooperat- Vsaid adjustable fulcrum being constructed and arranged so that the initial movement of said operating member in response to an.increase in temperature increases the contact pressure between said contact means and subsequent movement 'of said operating member in response to further increase in temperature causes said contact pressure to be decreased and said contacts to be snapped open under the influence of said resilient means.

19. Inv a temperature control device, a nxed contact, a resilient operating member xed at onel end and having its opposite end free to move, a movable contact normally engaging said xed contact to perform circuit controlling4 functions, said movable contact being actuated in accordance with movement of said free end of said v operatingy member, temperature responsive means associated with said operating 'member and adapteratingmember with a snap action between two limiting positions, means in said operating member adjacent said free end to increase the rigidity of said member to the thrust of said resilient means without increasing the weight of said member, control means actuated by movement of said operating member, means for constraining the movement of said operating member intermediate its ends comprising two fulcrums the rst of which is movable in response to temperature changes and the second of which is adapted to be engaged by said operating member after'a predetermined movement of said rst f ulcrumK in response to the occurrence of a predetermined temperature, and means for adjusting the position of said second fulcrum relative to said operating member to vary the constraining action of said second fulcrum so as to preselect the temperature at which said fulcrums cooperate to cause said control means to be actuated from one controlling position to the other under the inuence yof said resilient means.

22. A thermostatic switch comprising a flexible switch arm having one end restrained and its ed tol cause movement of said operating member Y in response to changes in temperature, and fulcrum means ior effecting the movement of said operating member to control the temperature at which said movable contact is moved out of engagement with said xed contact, said fulcrum means being constructed and arranged so that upon the initial movement of said operating memaccordance with an increase in temperature the contact pressure between said fixed and movable contacts is increased and upon subsequent movement oi' said operating member by said temperature responsive member in response to further increase in temperature the contact pressure between said xed and movable contacts is decreased and the movable contact is moved out of engagement with the fixed contact.

20. A. thermostatic switch comprising a iiexible switch arm having one end xed and its other end free to move, a spring acting .on said free end to apply thereto lateral force components without substantial longitudinal compression thereof to move said switch arm to one or the other of two controlling positions depending upon f the position of said switch arm, a fulcrum lying intermediate the ends of said arm and adapted to control the initiation of movement oi said arm from one controlling positionto the other'under the inuence of said spring, and a temperature responsive member for moving said switch arm with reference to said fulcrum so as to detery mine the controlling position of said armgin ac- 'ber by said temperature responsive member in tively thin operating member having oneend,

iixed and its opposite end free to move, a knife edge bearingon said free end of said member, resilient means bearing on said knife edgefor eiectingmovement of said free end of said opother end free to move, a resilient member acting on said free end to apply thereto lateral force components without substantial longitudinal compression thereof to move said switch arm to one or the other of two controlling positions depending upon the position of said arm, a fulcrum lying intermediate the .ends of said arm, a temperature responsive member for moving said arm into engagement withv said fulcrum so that said adapted to be actuated in accordance with the movement of said operating member, means for constraining said operating memberintermediate its ends comprising two fulcrums, the rst of which is movable in response to temperature changes and the second of `which is adjustable, means for adjusting said second fulcrum so asv to' vary its constraining action on said'operating member to predetermine the temperature at which said` control means are actuated by movement of said loperating member in accordance with movement of said rst fulcrum in response to temperature changes, and elastic means bearing on said operating member for effecting snap action movement of said member so that said control meansare actuated with a snap action.

2d. In a temperature control device, a resilient operating member having one end restrainedand its opposite end free to move, control means adapted to be actuated in accordance with movement of said free end of said operating member, means for constraining said operating member intermediate its ends comprising two fulcrums, the first of which is movable in response to temperature changes and the second of which is positioned to be engaged by. said operating memberv after a predeterminedmovement of said member inv accordance with the movement of said rst fulcrum, elastic means bearing on the free end-of said resilient operating member to effect ture at which said rst fulcrum causes said operating member to be actuated to one or the other of its limiting positions under the iniiuence of said elastic means.

WALTER R. MCDOWELL. RUSSELL A. WINBORNE. 

